Vulcanizable copolymers of acrylonitrile, butadiene and maleic esters



Patented a... 4, 1949 UNITED STATES PATENT OFFICE VULCANIZABLEcommunities or nonr- LONITRILE, nvrsmrmr: mm MALEIC ESTERS Gaetano F.DAlelio, Cleveland, Ohio. uslmor to Pro-phy-iac-tic Brush Company,Northampton, Mass, a corporation of Delaware No Drawing. ApplicationDecember 11, 1946,

.Serial No. 715,600

3 Claims. (Cl. 280-785) 1 This invention relates to new polymerizationproducts and is based upon the soovery that a and vulcanizable. Usei-ularticles can be iormed' from these copolymers by molding, extrusion orcalenderin'g. The properties oi these new copolymers depend upon therelative proportions of the ingredients from which they are made. Thus,

it is possible to prepare resinous compositions when the acrylonitrileis the major component. The maleicester appears to-serve as an internalplasticizer. I

When an acrylonitrileis used in an amount of about 35 per cent or morethe resulting copolymer has a high softening point and is dlfllcult toprocess by customary methods. In such cases, the copolymer may beprocessed by the method described and claimed in my copendingapplieation Serial No. 523,901, filed February 25, 1944, now U. S.Patent No. 2,425,086. The process described in that applicationcomprises forming a workable cohesive gel of the copolymer by mixingwith certain liquids, such as nitromethane. If a vulcanizablecomposition is desired, the vulcanizing ingredient-s may be incorporatedin the gel. The gel may be shaped to any predetermined form byextrusion, calendering or the like. Certain of these copolymers may alsobe improved as to physical properties by cold drawing accordingto themethods explained and claimed in said application.

In the practice of the invention I may use a butadiene-1,3 having theformula wherein R and R are a hydrogen or a hydrocarbon radical, forexample, methyl, ethyl, propyl, butyl, isobutyl, amyl, isoamyl, hexyl,cyclopentyl, cyclohexyl, methyl cyclohexyl, phenyl, tolyl, a chlorinesubstituted hydrocarbon, such as chlortolyl, chlorphenyl, and R isselected from the group consisting of hydrogen and methyl. and when R.is methyl, R is methyl and R is hydrogen.

Specific examples of the 1,3-butadienes are, butadiene 1,3 itseli;2-methyl butadiene-L3; 2,3- dimethyl butadiene-1,3; 2-methyl pentadiene-1,3 (2,4-dimethyl butadiene-1,3); 2-phenyl butadiene-1,3; 2,3-diphenylbutadiene-1,3; pentadlene-1,3; etc.

In the practice 01 the invention I may use an acrylonitrlle oi thestructure CH2=CRCN 5 wherein R is hydrogen or a methyl radical.

The monohydrlc alcohol esters oi maleic acid which may be used have thegeneral formula ROOCCH=CHCOOR m wherein It represents the residue of amonohydroxy alcohol; the only requirement of the alcohol is that itpossess at least one esteriflable hydroxyl group and is devoid ofethylenic and acetylenic saturation.

As examples or alcohols from which the maleic esters may be prepared, Iuse aliphatic monohydrlc alcohols. namely methyl, ethyl, propyl,isopropyl, butyl, isobutyl, amyl, secondary amyl, isoamyl, mixedamyl,and hexyl alcohols.

I am aware that reactions of tum-aric and maleic esters with other vinylderivatives have heretofore been known; for example, the Dlels- Alderreaction between a (Dene-1,3 and a maleic derivative, is well known inthe chemical literature.

As a typical example of the Diels-Alder reaction may be mentioned thereaction between butadiene and malelc anhydride. In this case a1,4-addition of the maleic anhydride to the butadiene occurs 40 When adiester of maleic acid, for example, diethyl or dimethyl maleate. isused, the corresponding ester oi tetrahydraphthalic anhydride isobtained, for example CH1 CH1 EH Oil-000R. 0 OH-OOOR H OH-O00R H OH-OOORv CH: O I

0 Butadiene Saturated mono- Saturated monohydrlo hydric alcohol alcoholdlester oi dlester oi malelo ten-ah dra hthalic acid ydi de Thesaturated monohydric alcohol esters of tetrahyd'raphthalic anhydrlde arenon-resinous, f non-plastic materials or low molecular weight.

of maleic acid have previously been known.

As a typical example mention may be made of the acryionitrile maleicanhydride and the acry- 'lonitrile diethyl maleate copolymers. Thesecopolymers are thermoplastic, non-vulcanizable compositionswhich-possess the structure according to the reaction as follows:

- err-=03 (OHFORON) (coon 0003);

, OH---OH-- em-mm) (000R 000R)- where the numerical value of n bears amoi ratio to m of at least one. Such copolymers are thermoplastic andsoluble and cannot be converted to the insoluble, infusible state. Onthe other hand. copolymers of acrylonitriie and maleic esters areprepared with extreme difllculty.

In view of the above chemical reactions, two things are surprising,First, that a tri-polymer results rather than a mixture of the reactionproduct of the Diels-Alder reaction and the acrylonitrile compound, andsecond, that the product is a typical resin being in one state solubleand fusible, and in a second state, i. e., after further polymerization,insoluble and infusible.

As stated, it is possible through the use of this invention to preparevulcanizable plastic compositions as for example when the acrylonitrilecomponent is in the major proportion. Such compositions are trulyresin-like, since they are capable of being molded without the additionof plasticizers; they are not rubber-like, since they are amenable tomechanical working, such as punching and drilling. If so desired, theymay likewise be cured with vulcanizing agents, thereby increasing theirsolvent resistance and their toughness.

Such compositions possess greater ductility than the correspondingcomposition of acrylonitrile and butadiene from which the maleic esterhas been omitted in the polymerization process. It is thereby seen thatthe compositions of this invention possess a greater utility than it ispossible to achieve by polymerizing separately the (1) acrylonitriiewith the butadiene, (2) the acrylonitrile with the diethyl maleate, or(3) the diethyl maleate with the butadiene. Example 1 indicates the widerange of polymers that may be obtained in the practice of thisinvention.

The objects of this invention are achieved for forming resinous productsby polymerizing a mixture comprising the ratios of about 50 to 90 partsof an acrylonitrile; about 5 to 30 parts of the butadiene-1,3 and about5 to 40 parts of the saturated monohydric alcohol ester of maleic acid.A preferred resinous product is obtained by polymerization of a mixtureof 15-20 parts of butadiene-1,3, 60-80 parts acrylonitrile, and 5-10parts of ethyl maleate. Depending on the proportions of the ingredientsused, compositions suitable as molding compounds which may be useddirectly in the preparation of molded parts or treated with vulc-anizlng0r curing agents.

The fumaric esters are not to be considered the equivalent of the maleicesters in the practice of this invention. As is well known, the fumaricesters are much more active and polymerize at a much higher rate thanthe maleic esters when used under active polymerization conditions. Whenfum-aric esters are used in conjunction with the dienes, largerquantities of the tetrahydrophthalic esters are formed by theDiels-Alder reaction than when the corresponding maleic esters are used.The tetrahydraphthalic esters do not copolymerize with the remainingingredients and thereby act as diluent plasticizers producing a softerpolymerization product only because of the plasticizer formed by thefumaric acid ester and the butadiene. This is not altogether desirablesince it is diflicult to remove the plasticizer from such compositions.It is further undesirable in the finished product, however, because nocontrol may be exercised on the amount of plasticizer added, and if afumaric ester of a lowboiling alcohol had been used, this plasticizermay be too fugitive to be permanently retained by the finished articles.The marked diflerenoe in the maleic and .fumaric esters is observed inthe preparation of the allyl esters of maleic and fumaric acid. Diallylmaleate may be readily distilled at low pressures of the order of 50mm., in the presence. of such active inhibitors as copper, withoutpolymerization of the mass in the distillation retort. On the otherhand, the distillation of diallyl fumarate in the same equipment andunder the same conditions and with the same amount of polymerizationinhibitor usually results in the loss of 50 to 70% of the diallylmaleate in the distillation retort. A more permanent internalpl-asticizing effect, 1. e. by copolymerization,

' is obtained when the maleic esters are used and become integral partsof the polymer molecule.

The internal plasticizing effect of the copolymerized monohydric alcoholester is sumciently high that no particular advantage appears to accruefrom the use of higher quantities.

Any suitable method may be used for the preparation of the polymers ofthis invention; however, emulsion methods are preferred. When my novelmaterials are prepared by emulsion polymerization, any substance may beused as the emulsifying agent, which, when dispersed in water containingthe polymerizable and other ingredients, is capable of producing apermanent dispersion of the reactive ingredients in water. The mostsuitable dispersion or emulsifying agents are those which give stableemulsions without promoting hydrolysis of the ester to any undesirabledegree.

Additional examples of emulsifying agents besides the sodium oieate usedin Example 1 are Ivory soap, the sodium salts of sulfonatedlongchain'alcohols, the water-soluble salts of sum)- succinic esters,N-stearyl betaine, cetyl trimethyl ammonium bromide, soluble ligninsulfonic acid salts, C-cetyl betaine, etc.

Usually a 2 to 4% solution of an emulsifying used when a weaker orstronger solution is desired.

Many of the polymers of this invention may likewise be prepared ingranular form and in this case agents which have relatively poordispersing properties whereby they form nuclei for the formation ofgranules of the tripolymers are used. Such agents are usually calledgranulating agents and this process may be defined as the method ofpreparing these copolymers in granular form which comprise dispersingthe polymerizablemixture in water by means of a protective colloid andpolymerizing the mixture under agitation. The concentration of thegranulating agent or protective colloid is adiustedso that it is notsubstantially greater than the amount of agent sufficient to maintainthe'polymerizable mixture in the dispersed phase while agitation ismaintained and is sufllcient to prevent adhesion or coagulaacme-1s tionof the dispersed merization process.

Examples of such protective colloids and granulating agents are solublestarch, methyl starch, polyvinyl alcohol, partially hydrolyzed polyvinylacetate,.gelatin, sodium halogenate, soluble'salts of cellulose,glycolate soluble salts of starch, glycol soluble salts of polyvinylalcohol glycolate, polymethacrylic acid, natural gums, etc.

Usually a concentration of 1 6 to 1% or a granulating agent in water issatisfactory. The quantities, however, are adjusted to the dispersingpower ;of the protective colloid.

As catalyst for the polymerization, I may use any effective oxygenliberating agent such -as benzoyl peroxide, sodium persulfate, potassiumpersulfate, sodium perborate, potassium perborate, hydrogen peroxide,stearyl peroxide. hyperoxldes, etc. -Any suitable amount of catalyst maybe used depending upon the nature of the catalyst. In general, between1% and 1- /2% of catalyst is used depending on the nature of thecatalyst and upon the desired rate of polymerization.

The course of polymerization of the monomeric mixture used in thepreparation of the polymers of this invention may be modifiedconsiderably by the presence of other ingredients used tomodiiy orcontrol the reaction. Thus, I may use small amounts of sulfur,hydroquinones; copper; naphthyl amine; carbon tetrachloride; pyrogallol;the higher mercaptans; the thiurams; the dithiurams; ferrous and ferricsalts such as the tartrates, citrates, lactates; finely dispersedmetals; halogenated amides; etc.

The ratio of the dispersed phase, that is, the mixture of thepolymerizable monomers, to the water used with the emulsifyingagentorprotective colloid as the dispersing phase, may be varied widely.Satisfactory results are obtained in the range of 100 parts of monomermixture to 100- 500 parts of the dispersing phase. Auxiliary organicsolvents, such as dioxane, ethyl alcohol. glycols, benzene, etc.. maylikewise be used in the presence of dispersed and dispersing phases.

These ingredients may be added directly to the polymerizable mixture ormay be present as diluents in the reacting ingredients. Thus, thehutadiene, as prepared by the catalytic dehydrogenation of the butenes,may contain some butane as well as some butene-l and butene-2.

Likewise, the acrylonitrile may contain definite quantities oflactonitrile or methacrylonitrile.

The maleic ester may likewise contain small quantities of a monoester asevidenced by the acid number of the technical grade materials.

The fundamental resins of this invention likewise may -be modified byother polymerizable monomers containing a single ethylenic polymerizabledouble bond. Illustrative examples of such compounds are the vinylhalides, e. g., vinyl chloride; the vinylidene halides, e. g.,vinylidene chloride, vinylidene, fluorochloride, etc.; the esters ofacrylic acid. e. g., methyl acrylate, ethyl acrylate, ethylmethacrylate, methyl methacrylate, methyl chloracrylate, fluorophenolacrylate, etc.; the substituted aryl ethylenes, e. g. bromotoluylethylene, etc.; the vinyl esters, e. g., vinyl acetate, vinylpropionate, vinyl butyrate, vinyl benzoate; methylene malonic esters;the monoalkyl esters, e. g., the methyl esters; the diesters, e. g., thedimethyl ester, the dipropyl ester, etc.; the allyl derivatives, e. g.,acrolein, methacrolein, vinyl methyl ketone, vinyl ethyl ketone, allylchloride, vinyl methyl ether, vinyl ethyl ether. vinyl propyl ether,allyl particles during the polyphenyl ether, allyl acetate, allylpropionate, allyl benzoate, etc.

If desired, the polymerization may be carried out as a masspolymerization, that is, the polymerizable ingredients are reacted inthe absence of dispersing agents or solvents. The preparation ofsuitable varnishes or coating compositions may be accomplished by theuse of organic solvents of the hydrocarbon and halogenated hydrocarbontypes. I

In any of the above polymerization methods, the reaction may be carriedout conveniently at 45 to 60 C. within a few days depending on thecompositionof the ingredients, the amount of catalyst, etc. It ispossible with higher catalyst concentrations or with increasedtemperatures to decrease the reaction time to five to seven hours.

When the gaseous derivatives of butadiene-l,3 are used, the highertemperatures are to be avoided. The choice of the polymerizationtemperature, as is readily seen, depends on the choice of ingredients,of catalyst, of ratio of the dispersed to the dispersing phases, and thetype of equipment employed.

The emulsified or dispersed polymers may be coagulated by any of themethods applicable to the dispersed polymer relative to the particularemulsifying or dispersion agent used. In many cases solutions ofaluminum sulfate are satisfactory when added slowly and with stirring.So

1 dium chloride solutions, preferably these conbut should a small amountof emulsion be obtained with the granular product, the resin containedin the emulsion may be precipitated by any of the means mentioned above.

In many cases where films or molded products of the copolymers of thisinvention are to be used unvulcanized and are required to withstandprolonged aging, it is desirable to add a small amount of antioxidant tosuch compositions. This is particularly true when the compositionscontain high amounts of acrylonitrile and are intended for use as anunvulcanized thermoplastic.

As suitable oxidation inhibitors may be mentioned N-phenyl beta naphthylamine, hydroquinone, eugenol, and similar substances, the amount neededbeing small, of the orderof s to 2% of the weight of the interpolymer.

Many of the copolymers of this invention are soluble in thenitrohydrocarbon solvents and as such are well adapted as film formingmaterials,

etc. These solutions may be used with or without vulcanizing or curingagents. When made in suitable equipment and under favorable conditions,the films are practically colorless. Furthermore, they are strong,tough, and flexible. Adhesion of these films to base materials such aswood, metal, glass and the like-is excellent. Such unpigmented solutionsare useful as clear varnishes, lacquers, coating compositions,adhesives. etc., whereas the pigmented solutions are suitable forcoating compositions such as paints and. pigcloth, cork, asbestos board,etc."

coating papers and textiles. cellular and other.

fibrous bodies, and porous or semi-porous materials to contribute totheir strength, toughness, imperviousness to moisutre, flexibility, etc.

The molding compositions prepared from such bodies, particularly thoseof a plastic nature rather than a rubber-like nature, possess theability to withstand bending pressures when such pressure is appliedslowly.

These compositions are ideally suited for the preparation oi articlesthat are usually subjected to bending strains, such as combs or wiringof electrical equipment, panel boards, leather, etc.

The polymers of this invention containing in general less than 50% ofbutadiene are of the nature of ductile synthetic resinous compositionsFillers and reinforcing a'gents and diluents may be used such as woodflour, cotton flock, alpha flock, mica, asbestos, silica, powderedquartz. bagasse, lignocellulose. hydrolyzed wood. magnesium oxide,magnesium carbonate, clay, lithopone, limestone, etc.

.In order that those skilled in the art better may understand how thepresent invention may be carried into effect, the following examples aregiven by way of illustration but not by limitation.

Example 1.

able monomer to about 50 parts of 5% sodium oleate solution in distilledwater. As polymerization catalyst there was used 0.25 part of potasslumpersulfate in the presence of 0.5 part of steel capable oi beingvulcanized in the usual fashion to yield cured compositions withincreased heat and solvent resistance.

For example, a resin-like product may be made by copolymerizinga mixtureof about 50 to 90 parts of an acrylonitrile, about 5 to 30 parts of abutadiene-1,3 and about v5 to 40 parts of a saturated monohydric alcoholester of maleic acid.

The compatibility of these new compositions with plasticizers is higherthan that of the normal acrylonitrile-butadiene composition. This isattributed to the fact that the ester groups of maleicderivatives whichhave interpolymerized with the other ingredients ofier widerpossibilities in the selection of suitable plasticizers.

Among the plasticizers suitable for use in this invention are dicresylphosphate, dibenzyl seba cate, dibutyl sebacate, diethylene glycoldihexoate, dibutoxy ethyl sebacate, dicrotyl azeleate, tributyl citrate,triacetone, tetraethylene, chlorinated diphenyls, octyl phthalate,clciohexoadipate, benzyl borate, dibenzyl ether, octyl chlorbenzoate,glycerol trilevulinate, ethylene glycol butyl phthalate,tetrachydrofurfuryl sebacate, tetrachydrofurfuryl fumarate, tributylaconitate, etc. A wide variety of plasticizers may be used because ofthe solvation effect of the malelc ester group in the tripolymer.

The fundamental products of this invention may be likewise compoundedwith other synthetic resins and other synthetic rubbers. They may beblended with the unsaturated alkyd resins, plasticized polyvinylchloride resins, the polyvinyl acetal resins, with pigments, fillers,dyes, lubricants, softeners, etc. v

The vulcanization of these polymers may .be accomplished in the standardmethod of vulcanizing natural or synthetic rubber with or withoutreinforcing agents such as carbon black, etc.

As accelerators in conjunction with sulfur there may be used thealdehyde amines, the guanidlnes, the carbon disulfide derivatives ormixtures of such materials. Some typical examples areheptaldehydeaniline, butyraldehyde butyl amine, diphenylguanidine, di otoluylguanidine, triphenylguanidine, zinc dimethyl dithiocarbamate, zincdibutyl dithiocarbamate, tetramethyl thiuram disulfide, tetramethylthiuram monosulflde, mercapto benzothiazole, zinc mercaptobenzothiazole, benzothiazole disulfide, etc.

These material may also be vulcanized without sulfur through the use-ofnitro compounds and organic peroxides such as trinitrobenzene,tetranitronaphthylene, benzoyl peroxide, 8. mixture of benzaldehyde andmercuric oxide, halogenated benzoquinones, benzoquinone dioxime, etc.

wool as an activator and moderator of the reaction. The polymerizablemixture was introduced into pressure vessels and reacted at 50 C. for atleast 12 hours. An oxidation inhibitor, namely N-phenyl beta naphthylamine was added to the resulting latex before precipitation with anaqueous 5% sodium chloride solution containing 2% sulfuric acid. Thegranulated polymers were washed free of soluble material, dried in avacuum 'oven and milled on rolls. The ratio of the polymerizablecomponents is given in the follow- .ing table:

Specimen Acrylonitrile 8 2 2 Butadieno so 10 so 40 10 so so 10 40 oo 10so so 20 so on so 10 7o 15 1o 5 15 so 10 1o so it) 5 All of the abovepolymers were vulcanizable, even those containing small quantities ofbutadiene. The types of polymer obtained were as follows whereinspecimens A and B are recited for comparison:

Characteristics g. Similar to C but less yielding. Similar to 0. Tough,more yielding than E. Tough, more ductile than I". Tough, than Verytough, harder than H. Tough, softer than and similar to 1.

Example 2 Vulcanized products of high utility were obtained byprocessing samples 13, D, E, and F using the following as a ratio ofcomponents:

These compounds were cured at C. for 30 minutes. In compositionscontaining 40 or more per cent of acrylonitrile, compounding oi the c075 polymers may be accomplished by gelling the copolymers withnitromethane which was removed before molding as described in mycopending application Serial No. 523,901, filed February 25, 1944. Theproducts varied from rubbery bodies to hard, tough molded specimens. Theintroduction of the vulcanizing ingredients may be accomplished by theintroduction of these ingredients into the latex prior to precipitation.

Example 3 A varnish solution of the tripolymer of specimen J wasprepared by dissolving the tripolymer in benzene to give a 30% solutioncontaining one part of Altax and two parts of sulfur. This varnishsolution was used directly as a vulcanizable coating for wood, glass,and as an impregnant and coating for paper, fabric, etc. The adhesion inall cases, even to glass, was excellent.

Example 4 The following ingredients werereacted for 24 hours at 6 5-70C. in steam jacketed reactor equipped with stirrer, etc.

Parts Aerosol T (a dioctyi ester of sodium sulfosuccinic acid) 25Distilled water 500 Acrylonitrile 60 2-methyl pentadiene-1,3 20 Diethylmaleate 20 Potassium persulfate 0.5

1. A resinous copolymerization product of a mixture of 15-20 parts ofbutadiene-1,3, 60 to 80 parts acrylonitrile, and to parts of ethylmaleate.

2. A resinous copolymerization product of a mixture comprising 50 to 90parts of a compound selected from the group consisting of acrylonitrileand methacrylonitrile, 5 to parts of a compound having the formula whereR and lit are selected from the group consisting of hydrogen, alkyl,aryl, chloraryl and a cycloaliphatic radical which is free of ethylenicunsaturation and R is selected from the group consisting of hydrogen andmethyl, and when R is methyl, R is methyl and R is hydrogen, and 5 toparts of a diester, said diester being the esterification product ofmaleic acid and an allphatic monohydric alcohol which -is free ofethylenic and acetylenic unsaturation.

3. The product resulting from sulfur vulcaniza tion of the resinouscopolymerization product of a mixture comprising to parts of a compoundselected from the group consisting of acrylonitrile andmethacrylonitrile, 5 to 30 parts of a compound having the formulaaliphatic monohydric alcohol which is free of ethylenic and acetylenicunsaturation.

GAETANO F. DALELIO. REFERENCES CITED The following references are ofrecord in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,266,794 Panwitz et al. Dec. 23,1941 2,374,841 Bemon May 1, 1945

